The home of the Big Mac, which already sells a Vegetarian Deluxe burger, has signed a deal with Quorn manufacturer Marlow Foods to supply its restaurants with burgers.
Quorn, which predominantly targets women, already provides McDonald's rival Wimpy with burgers; it is not known whether the McDonald's deal with will affect this relationship.
A McDonald's spokeswoman said that the company has been speaking to a variety of companies about developing another vegetarian burger, but added that it would not comment on commercially sensitive speculation.
The Quorn burger is likely to be promoted by McDonald's advertising agency Leo Burnett, but no one at the agency would comment.
Future marketing activity for the burger will focus on the healthy and meat-free credentials of Quorn. Recent campaigns from McDonald's have emphasised the quality of its products.
The launch comes as the chain adopts a healthier image to improve declining sales. It recently introduced fruit to its menu and now provides detailed nutritional information on its foods.
Quorn is the market leader in the £582m meat-free market and has a market share more than twice that of its competitors combined.
The tie-up comes in the wake of a change in strategy at Quorn. In 2003, it launched outdoor, radio and press work through J Walter Thompson targeting non-vegetarians. It used the strapline "Smart eating starts here", with creative focusing on facts about Quorn, such as its sausages containing 80% less fat than normal sausages.
In May 1997, Wimpy became the first fast-food chain to offer Quorn burgers. Burger King already offers a Spicy Bean Burger and Vegetarian Whopper.
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